Electric test device



June 3, 1952 J FISCHER 2,598,775

ELECTRIC TEST DEVICE Filed May 11, 1951 //\/A/E/\/ 7-572 EDWARD J. HSCHER "pr" o Patented June 3, 1952 UNITED STATES PATENT OFFICE ELECTRIC TEST DEVICE Edward J. Fischer, Vancouver, Wash.

Application May 11, 1951, Serial No. 225,734

2 Claims.

My invention relates to devices for testing electric circuits and has particular application to cate to the installer just how the receptacle is mis-connected in case the receptacle is not connected properly to the house service.

It is a third object of my invention to insert a fuse in each of the ungrounded wires of the range service circuit so that in case. the range or any of its parts are not properly connected no damage will be done and the trouble can be quickly found and the connection restored without having to hunt up the main supply box to replace a fuse.

It is a fourth object of my invention to provide such a device which is low in first cost, rugged in construction, of relatively small size,

having a form making it convenient to use, and

particularly adapted to the testing of the common type of single phase three wire circuit having one of the wires at ground potential and with the other wires at potentials of equal instantaneous magnitudes but of opposite instantaneous polarities.

How these and other objects are attained in the device of my invention is made clear in the following description referring to the attached drawing in which Fig. 1 is a perspective view of one form of my device between a range service receptacle and a range cord plug with which it is used.

Fig. 2 is a diagram showing the circuit relations of the active elements of the device of Fig. 1.

Fig. 3 is a simplified schematic diagram of the device of Figs. 1 and 2, showing the electric potentials applied to the elements of the device when the device is plugged into the house circuit receptacle and the receptacle is properly wired in the house circuit.

Fig. 4 is the same as Fig. 3 but with the house circuit mis-connected to the receptacle so that the ground wire is interchanged with one of the energized wires.

Fig. 5 is the same as Fig. 4 but with the house circuit mis-connected to the receptacle so that the ground wire is interchanged with the other of the energized wires.

Referring now to the drawings, in Fig. 1 is shown, without the simple and well-known details of construction and wired in accordance with Fig. 2, an insulating body B having inset conducting receptacle elements Rl R2, and G, in one end and conducting plug prongs El, E2, and G, extending from the other end. A receptacle for plug fuse Fl is wired between prongreceptacle RI and prong El. A receptacle for plug fuse F2 is wired between prong receptacle R2 and prong E2. Prong G is wired to prong receptacle G.

A single pole double throw switch having a conducting blade SG biased tonormally contact with terminal SN but operable by pressure applied to insulating switch stem S to leave terminal [SN and make contact with terminal S2, is mounted within insulating body B in such a manner that stem S is exposed for manual manipulation in the recess shown in the top of body B.

A receptacle for indicating lamp L1 is wired between prong receptacle RI and terminal SN. A receptacle for indicating lamp L2 iswired between prong receptacle R2 and terminal SN. 7 A receptacle for indicating lampLG is wired between prong G and blade SG. Prong receptacle R2 is wired to terminal S2.

Lamps LI and LG are selected for operation at the normal effective potential between either'of the prongs El, E2, and the prong G. v

In use the device is pushed in place with the prongs El, E2, and G entered in the mating receptacle of the house circuit, it being understood that both the plug and receptacle ends of my device as well as the house circuit receptacle and the range plug to be connected thereto are polarized by the relative positioning of the prongs of the plugs and the prong receptacles of the plug receptacles so that the plugs can enter the receptacles in only one arrangement of contacts.

With my device thus in test positiontheelements of the device are subjected to, the potentials of the house circuit as shown in Figs. 2 and 3 if the house receptacle is correctly wired or as in Figs. 3 or 4 if the house receptacle is incorrectly wired. Referring to Figs. 2 and 3, if the house receptacle is correctly wired, lamps Ll and L2 in series will be subjected to the potential across prongs El and E2 which will be the sum of the potentials across El, G and E2, G, or twice the potential across either El or E2 and G. Since all of the lamps are alike and designed to operate on the potential across El or E2 and G, both lamps LI and L2 will come up to full brightness. As seen, lamp LG will be at ground potential on either side and will not light up. Then to be sure that lamp LG is not defective, lamp LG is tested by depressing switch stem S causing blade SG to leave terminal SN and contact with terminal S2. Now lamp LG is subjected to the potential across E2 and G and comes to full brightness indicating that a true indication was previously given, and ,:the house receptacle. was wired correctly.

However, if the house receptacle was not correctly wired so that, when my device is plugged in, the potential arrangement is as shown in Fig. 4 as though prongs El and G had-been interchanged, the potential across lamps. ,L2,and LG inseries will be the full line to line potential and lamps L2 and LG will come; upto fullbr-ightness, while lamp Ll, having ground potentialgat both terminals, will remain dark. If it is de- ,.,sired,in this case totesttheoperability of lamp "Ll,stems isjdepressedgonl enoughsto break the bination of a polarized three prong plug and mating three prong ,plug receptacle adapted to form a connector in said connection, together with a testing device adapted to be inserted in said service connection between said plug and said receptacle, said testing device comprising an insulating body, three conducting plug prongs v- =secured to tandeextending from said body and i mactlof blade';SG with'terminalSN at which ;,,t i rne,lamp, LG will go dark and lamp LI and L2 ..will .light;.egually ,butjdimly since each will be subjectedt only;,hali,of its normalpotential.

';Sih1ilarly as indicated infFfig. 5, the house receptacleuhasbeen miss-:connected by having ...the., ground wirehconnected .to, the receptacle so Lthatit wouldmake connection inthe normalEZ v -D0sition,.1amp,Ll and LG would show equally at full brightness andLZ would remain dark.

vltris,--therei ore, seen that mydevice' is thoronghlyefiective inlocatinguthe position of the w groundwire in the wiring ,tothehouse receptacle 7.

and if the ground wirebofmtheghouse. circuit is .,connected.torntheri hanthe ground terminal of .thehousenircuit.re eptaclerthe wir n chan to ,besmaldegtoporrect the 'difiiculty is plainly indicated. V

gMZhen lit isldetermined that thef house circuit receptaeleis .cerr ct wired, then the ran e.,. ue ;is,-. inserted intortheg. receptacle. end of myldevice, iaftenewhichthe various circuits of the range are individually turnedionandioffi, to be. sure of their decorrecthpperation. ShOl.1ldthe wiring of the range be defective in suchiagway, as tofthrow; an eexcessiyeeload on.-..thei,line, ,onev of the fuses Fl aoriliof my .devicewill'blow to isolate the, circuit so that it canbeexamined and'the'idiificulty cor- ,rected. Afterthis. the.low-,costjj,use in my device ,maybe replaced andrthe rangev testing resumed. l-laving thus-completelyjdescribed .one ,form of .;the, device,v 0f,.my, inyentionrandnclearly explained .its.,.use,: I claim:

1., [n-.,the vvcomman type,..of, three wire service ,comiectionsetov anwelectric range, ,or' the like,

. ,wherein. the electric seryice is. of the three wire .erounded neutral typeflhaving the neutrally designatedwire at ground potential and and each i of the other wires at other than ground potential and wherein the potential between said other unresisequaliothe, sum of the individual potenhtialsrhetweeneach of'them andgroundnthe comadapted-:to,mateiwithcsaid receptaclenthree conducting plug prong receptacles inset in said body and adapted to mate with said plug, a pair of fuse receptacles inset in said body, three lamp recep- =tacles inset in said body, a single pole double throws.-switch-Jsecured to said body, a first circuit means connecting the neutrally designated l oneiof said-tthreeprongs to the neutrally desigondi'one :of said three prongs-to asecond, one. of l said threeprong-receptaclesthrough a fuse in .One of said" fuse: receptacles andtoione terminal third circuit means connecting the third "one or said three prongs "tothethird-one'of said three prong-receptacles through-a'fuseinthe other of said fuse: receptacles, ftOTODGftGImiHa]. of the third of said three lamp receptacles and to one point of said-switch; a fourth circuit means connecting the blade of said switch "to the other terminal: of "said first "lamp receptacle, 4 and" a fifth circuit means-connecting the other point of' said switch to the other terminalsbtboth said 'sec- 0nd ,and third lamp-receptacles.

. 2. For insertion between the; polarized; plug and receptacle ina'king; connection between athree tween said other .two wires,,1means'for 'connecting the commonterminal' of a single .pole' double throw switch'tosaid neutral wirethrough aithird electric lampgmeans. for connecting onefthrow iterminaliofsaid switch to one of said/other wires, and means for connecting the -other throw terminal of said switch to the connection between said pair of lamps.

EDWARD J. FISCHER.

*REFERENCES l CITED The following references are-"of recordlinthe file of this patent:

V UNITED *STA'IES: PATENTS 2,548,991 McNabb Apia-7,1951 

